JPH0690470A - Pcm codec (coder and decoder) integrated circuit of electronic exchange - Google Patents

Abstract

PURPOSE: To provide a PCM CODEC integration circuit of an electronic exchange which eliminates noise signals. CONSTITUTION: This device is constituted of a buffer 11', a signal-selecting part 12' which checks abnormality of a PCM highway side line, a sending end gain controlling part 13', an antialiasing filter 14' which considers sampling of a subsequent stage and prevents noises, a charging signal eliminating part 15' that eliminates a feedback element of a charging signal, a band-pass filter 16' which makes only a voice signal band signal pass through, a coder 17' that exchanges an analog signal and a PCM output signal, a decoder 18', a low-pass filter 19', a receiving end gain controlling part 20', a smoothing filter 21' which attenuates high-frequency signals in the step wave form which is generated when the lowpass filter is realized through switched capacitor, an operational amplifier 22' which drives a line subscriber line and a charging gate 23' that connects a signal of a charging signal source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse code modulation (PCM) signal processing integrated circuit of an electronic exchange, and particularly in a public telephone or the like, a chip (Tip) and a ring (R) are used at the time of billing.
ing) reverses the polarity of the power supply and charges it by sensing it, and an unnecessary noise signal is generated when the polarity is reversed. Therefore, in order to remove this noise signal, the charging signal PCM of an electronic exchange with a built-in filter that removes the charging signal induced to the transmitting side during use
CODEC (pulse code module)
on coder and decoder) integrated circuit.

[0002]

2. Description of the Related Art Generally, a conventional PCM electronic exchange PC
The M signal processing circuit is configured as shown in FIG.
That is, the interface circuit unit 1, the billing signal removing unit 2, the billing signal combining unit 3, the impedance matching unit 4, and the PCM.
PCM signal processing circuit I including CODEC integrated circuit 5
Depending on the number of subscribers (n), a large number of C ₁ -IC _n (n
PCM signal processing circuit IC ₁
-In IC _n , the PCM highway (PCM Highway
The common bus 7 referred to as y) and the billing signal source 8 are connected to each other, and when the billing is required, the billing signal of the billing signal source 8 is synthesized by the billing signal synthesizing unit 3 when the billing is required, and the interface circuit unit 1 has a configuration for supplying the same.

In addition, the PCM CODEC integrated circuit 5
As shown in FIG. 2, the signal selecting unit 11 and the signal synthesizing unit 1
2, the transmission side gain control unit 13, the anti-aliasing filter (AAF; Anti-aliasing filter)
r) 14, band pass filter (BPF) 15, coder 1
6, a decoder 17, a low pass filter (LPF) 18, a receiving side gain control unit 19, an operational amplifier 20, a hybrid balance filter (hybrid balance fi).
lter) 21 and a gain controller 22.

[0004]

In the conventional PCM signal processing circuit having the above structure, the voltage applied to the chips T ₁ -T _n and the rings R ₁ -R _n on the line side of the line subscriber. It will reverse the polarity of, and will calculate the call charge with a clicking sound. At this time, in order to eliminate the click sound, a charging signal of a sine wave can be applied without inverting the polarity of the voltage.
The billing signal (12 KHz or 16 KHz) is combined with the signal in the voice region on the transmitting side, and unwanted signals are converted into PCM by signal distortion and modulation. Therefore, when billing with an analog signal, unnecessary charging signals are removed from the transmitting side. There must be. Specifically, among the characteristics of the interface circuit section 1 which is the line of the line subscriber, the function of the hybrid 2/4 line conversion device as shown in FIG. 3 causes the reception side (Rx),
That is, the signal output from the terminal AO of the PCM CODEC integrated circuit 5 causes the current i ₁ to flow in the coil L ₁ . As a result, an induced current i ₂ is induced in the line side coil L ₂ of the line subscriber, and this induced current i ₂
As a result, a new induced current i ₃ is induced in the coil L ₃ on the transmitting side (Tx), and an unnecessary sinusoidal charging signal which is not actually desired is transmitted to the transmitting side (Tx). In order to remove such an unnecessary charging signal, the conventional PCM C shown in FIG.
In the ODEC integrated circuit, the PCM CODEC integrated circuit 5
Among the signals output from the terminal AO, only the signal in the audio signal band is compensated by creating a signal having a polarity opposite to the induced current i ₃ induced on the transmission side (Tx) by the hybrid balance filter 21 and the gain control unit 22. However, the charging signal synthesizing unit 3
Since the billing signal output from the PCM CODEC integrated circuit 5 cannot be removed, the billing signal removing unit 2 which is an application circuit outside the integrated circuit is required.

As described above, the PCM CODEC integrated circuit 5 in the conventional PCM signal processing integrated circuit having the billing signal removing unit 2 and the billing signal synthesizing unit 3 has the voice signal band of all the input signals including the noise signal. by selecting only necessary signal to the PCM signal, that is, it becomes converted into a digital signal, the induced current i ₃ to the transmission side (Tx) by induced signal components to the receiver (Rx) shown in FIG. 2 After measuring the value induced as, the characteristics of the hybrid balance filter 21 and the gain control unit 22 are fixed, and the induced current i ₃
As a result of producing a signal having a characteristic opposite to that of the signal synthesis section 12 and synthesizing the signal, the resin side (Rx) of the voice band to the transmission side (T
The inductive component to x) is somewhat reduced, and the gain control unit 13 on the transmission side adjusts the change in gain generated through the charging signal removal unit 2 and the impedance matching unit 4 shown in FIG. Then, the anti-aliasing filter 14 removes the frequency band used by the sampling circuit in the band-pass filter 15 and the aliasing reduction of the voice signal, and the band-pass filter 15 eliminates unnecessary components other than the voice band. After removing the signal, only the signal (analog) in the required voice band is converted into a PCM signal by the coder 16, that is,
After being converted into a digital signal, the signal is put on the PCM highway which is the common bus 7 at a predetermined time. However, when there is a billing signal, the billing signal is generally distorted in the public telephone network due to the characteristics of a general subscriber line. Therefore, the magnitude of the signal of the billing signal source 8 is usually several V (Volts) or more. If there is no billing signal removing unit 2, the billing signal induced to the transmission side (Tx) is input at several hundred mV, becomes a signal larger than the voice signal, and causes distortion and modulation of the voice signal. The signal removing unit 2 must be provided.

Therefore, the PCM CODEC integrated circuit 5
Since a special application circuit such as the billing signal removing unit 2 is used in the vicinity of, the peripheral circuit becomes complicated. Therefore, the addition of such an application circuit has a drawback in that, when the number of subscribers mounted per subscriber board increases, not only the board layout and wiring are difficult but also the reliability is lowered.

The present invention is a PC of the above-mentioned conventional electronic exchange.
The PCM COD is designed to eliminate the drawbacks of the M signal processing circuit, and includes a billing signal removing unit for eliminating distortion and modulation of the transmission signal generated by the billing signal.
By embedding a simplified subscriber board by incorporating it in an EC integrated circuit, a large number of lines can be accepted per unit subscriber board, and a PCM of an electronic exchange that enables a caller to make a high-quality call. Its purpose is to provide a CODEC integrated circuit.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. P of the present invention for achieving the above-mentioned object
CM CODEC integrated circuit, switch the telephone line and signal interface to the interface circuit unit 'n pieces of PCM signal processing circuit IC ₁ consisting of' 1 'and the impedance matching section 2' and the PCM CODEC integrated circuit 3 -I of
C _n 'and a common bus 4'called a PCM highway, which commonly uses the line usage time of telephone subscribers in a time division manner, a charging signal source 5', and a CPU 6'which controls a telephone call of an n-line subscriber. It has a configuration provided.

Further, the PCM CODEC integrated circuit 3 '
Is a buffer 11 'for obtaining a high input impedance
And an analog loopback (Analog Loopb) to check the abnormality of the line on the PCM highway side.
ack), a signal selection unit 12 ′, a transmission side gain control unit 13 ′ that compensates a gain generated when a circuit for matching the regulation on the subscriber line side is realized, and noise in consideration of sampling in the subsequent stage. An anti-aliasing filter (AAF) 14 'for preventing, a billing signal removing unit 15' for removing a feedback element of a billing signal, and a band-pass filter for passing only a signal (300 Hz-3.3 KHz) in a voice signal band. Unit (BPF) 16 ', a coder (CODER) 17' for converting an analog signal into a PCM output signal, and a PC
Decoder 18 'for converting an M input signal into an analog signal
A low-pass filter (LPF) 19 'that passes only a signal in the audio signal band (0 Hz to 3.3 KHz), a reception-side gain control unit 20' that compensates the reception-side gain, and the low-pass filter. The filter 19 'is replaced by a switched capacitor (SC; S
a smoothing filter 2 for attenuating a high-frequency signal in the form of a staircase wave that is generated when it is realized by a Witched Capacitor 2
1'and an operational amplifier (OP AMP) 22 'which enhances the signal driving capability so that the line subscriber line can be directly driven.
And a charging gate 23 'for connecting the signals of the charging signal source 5'.

FIG. 4 shows the PCM CODEC integration circuit of the present invention.
Example of a PCM signal processing circuit of an electronic exchange using a path
And FIG. 5 is a PCM CODEC integrated circuit of the present invention.
In the block diagram of the
Then, as shown in FIG. 3, the voice signal for the call is subscribed.
Induced current i on the main line side₂Is induced, and this induced current i ₂
Is the induced current i on the transmission side (Tx)₃To induce
It This induced current i₃Signals by PCM CODEC
It is applied to terminal AI of integrated circuit 3 '. At this time, terminal A
The signal applied to I is a chip (T; Tip) and a ring.
The audio signal from the (R; Ring) side is
It is generated from the power source noise from the source and before it is input to the terminal AI.
White noise (White noise) and the receiving side (R
x) to i₁→ i₂→ i₃Recipient Induced in the Path
It is composed of components such as the origin component (voice signal band and billing signal).
Is made. Therefore, the PCM CODEC integrated circuit 3 '
Is the only signal in the signal component that requires the audio signal band
To convert to a PCM signal, that is, a digital signal
And applied to the PCM CODEC integrated circuit 3 '.
The signals to be output are the buffer 11 'and the signal selection unit 12'.
After that, it is applied to the transmission side gain control unit 13 '. Do so
Then, the transmission side gain control unit 13 ′ joins the input signal.
To compensate the signal gain to meet the regulations on the main line
In this way, the gain meets the regulation on the subscriber line side.
The signal that becomes like this is the anti-area single filter 1
4 ', charging signal removing unit 15', and band-pass filter 16 '.
Through which unnecessary signals are removed. Anti here
The aliasing filter 14 'is the charging signal removing unit 1 in the subsequent stage.
5'and the band pass filter 16 'when sampling
Removes the signal generated by pulling, that is, bandpass
Used because the sampling circuit is adopted in the filter 16 '
Eliminates the frequency band and aliasing phenomenon of audio signals
The billing signal removing unit 15 'removes the feedback element of the billing signal.
I will leave. In this way, the bandpass filter 1
Audio signal band that passed 6 '(300Hz-3.3KH
z) is the PCM output signal (digital
Common signal 4) at a fixed time
It is placed on a certain PCM highway and transmitted to other subscribers.
To be done. On the other hand, the PCM output signal input to the receiving side (Rx)
Signal is converted to an analog signal by the decoder 18 ',
Of the audio signal band passed through the low pass filter 19 '.
Only the signal (0Hz-3.3KHz) is the gain controller on the receiving side.
20 'to apply the characteristics of the interface circuit section 1'.
Considering this, the signal gain is compensated in advance. like this
The signal whose gain is adjusted to the smoothing filter 21 '
Input and reduction reduction consisting of switched capacitors
The high frequency signal of the staircase form generated from the filter 19 '
After the attenuation, the calculation increase that can drive the line subscriber line directly
The impedance matching unit 2'and the interface are connected through the width device 22 '.
It is transmitted to the subscriber line through the face circuit section 1 '.

Here, the billing gate 23 'is provided so that a signal for billing processing and a voice signal to be supplied to the line subscriber can be combined and supplied only by a simple resistor, and can be supplied at a desired time. Signal from CPU 6 '(MSSYNC)
Since the billing signal source 5'is connected and disconnected in response to a command, it is possible to minimize the elements necessary for constructing the entire telephone subscription line.

FIGS. 6A to 6C show modifications of the PCM CODEC integrated circuit according to the present invention, and FIGS. 6A and 6B show the PCM C shown in FIG.
The signal selection unit 12 'and the coder 1 in the ODEC integrated circuit 3'
7 ', the arrangement order of the respective circuit portions formed between the 7'and 7'is replaced.

Also in this case, each of the circuit parts can operate similarly to the circuit parts corresponding to the circuit shown in FIG. 5 to remove the unnecessary charging signal.

Further, FIG. 6C shows the female PCM COD shown in FIG.
This is an example in which the transmission side gain control unit 13 'and the bandpass filter 16' are realized by one digital filter and transmission gain adjusting unit 30 in the EC integrated circuit 3 ', which is also shown in FIG.
The operation is similar to that of the ODEC integrated circuit 3 '.
On the other hand, normally, the band pass filter 16 'and the coder 17' process analog signals or digital signals. In this case, SCF (S
Witched Capacitor Filter)
Signal processing is performed by SDM during digital signal processing.
Signal processing is performed by (Sigma-Delta Modulation). In the charging signal removing unit 15 ′ having the SCF structure, the charging signal removing unit 15 ′ and the analog signal band-pass filter 16 ′ have the same sampling clock (Sampling).
Clock), or the charging signal removing unit 1
The clock frequency of 5'is doubled or quadrupled,
White noise generated from the whole circuit configuration is 1/2 or 1 /
It can be reduced to 4.

[0015]

The PCM of the present invention which operates as described above.
In the CODEC integrated circuit, a filter for removing the charging signal is built into the PCM CODEC integrated circuit, and unnecessary charging signals at the time of charging are removed. It has the advantages of being capable of accepting the lines of the above, and reducing the noise generated by the signal distortion and the modulation due to the charging signal and enabling the caller to make a high quality call.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a PCM signal processing circuit of an electronic exchange using a conventional PCM CODEC integrated circuit.

FIG. 2 is a detailed block configuration diagram of a conventional PCM CODEC integrated circuit.

FIG. 3 is a diagram showing modeling of a 2/4 line conversion function of the functions of the interface circuit units 1 and 1 ′ which are line subscriber matching units.

FIG. 4 is a diagram showing an embodiment of a PCM signal processing circuit of an electronic exchange using the PCM CODEC integrated circuit of the present invention.

FIG. 5 is a detailed block diagram of the PCM CODEC integrated circuit of the present invention.

6A to 6C are respectively PCM C of the present invention.
It is a figure which shows the modification of an ODEC integrated circuit.

[Explanation of symbols]

 1 interface circuit part 2, 15 'billing signal removal part 3 mixer 4 impedance matching part 5 integrated circuit 6' subscriber control signal 8 billing signal source 11 'buffer 13' transmission side gain control part 14 'anti-aliasing filter 16' band Pass filter 17 'Coder 18' Decoder 19 'Low pass filter 20' Receiving side gain controller 21 'Smoothing filter 22' Operational amplifier

Continuation of front page (72) Inventor Kiyoshi Yu, Republic of Korea, Gwangmyeong-si, Gwangmyeong-si, Mt.

Claims (8)

[Claims] 1. An n number of PCM signal processing circuits IC ₁ ′ -IC _n ′ comprising an interface circuit section 1 ′ for interfacing a mutual signal between a switchboard and a telephone line, an impedance matching section 2 ′, and a PCM CODEC integrated circuit 3 ′. When,
A common bus 4'called a PCM highway, which commonly uses the line usage time of telephone subscribers in a time division manner, a charging signal source 5 ', and a CPU for controlling a telephone call of an n-line subscriber
In the PCM signal processing circuit of the electronic exchange comprising 6 ', the PCM CODEC (Pulse Code)
Modulation Coder and Deco
der) The integrated circuit 3'has a buffer 11 'for obtaining a high input impedance, and an analog loopback (Ana) for checking a line abnormality on the PCM highway side.
signal selection unit 1 using log loopback)
2'and a transmission side gain control unit 13 'for compensating the gain generated when a circuit for matching the regulation on the subscriber line side is realized.
An anti-aliasing filter (AAF) 14 'for preventing noise in consideration of sampling in the subsequent stage, and a billing signal removing unit 15' for removing a feedback element of the billing signal.
And a signal in the audio signal band (300 Hz-3.3 KHz)
A band-pass filter (BPF) 16 'for passing only
A coder 17 'for converting an analog signal into a PCM output signal.
And a decoder 18 'for converting the PCM input signal into an analog signal, and a signal in the audio signal band (0 Hz-3.3 KH
low pass filter (LPF) 19 'for passing only z)
And a receiving side gain control unit 20 ′ that compensates the receiving side gain.
And a smoothing filter (Smoothing Filter) for attenuating a high-frequency signal in the form of a staircase generated when the low-pass filter 19 'is realized by a switched capacitor (SC).
er) 21 'and an operational amplifier (OP AMP) 22' for processing a signal so as to directly drive the line subscriber line.
And a charging gate 23 'for connecting the signal of the charging signal source 5', the PCM of the electronic exchange.
CODEC integrated circuit. 2. The PCM C of the electronic exchange according to claim 1, wherein a sine wave signal is used as the charging signal.
ODEC integrated circuit. 3. The charging signal control unit 15 ′ is SCF (Swi
The signal is processed by a tched Capacitor Filter or SDM (SigmaDelta).
2. The PCM CODEC of the electronic exchange according to claim 1, wherein the signal is processed by the modulation.
Integrated circuit. 4. The PCM CODEC integrated circuit of the electronic exchange according to claim 3, wherein the frequency of the signal removed by the billing signal removing unit 15 'can be selected according to the billing signal source by an external pin or selection information. . 5. When the billing signal removing unit 15 ′ processes the signal by the SCF, the frequency of the signal input to the billing signal removing unit 15 ′ is set higher than the sampling clock frequency of the bandpass filter 16 ′ to reduce the total noise. 4. The PCM CODEC integrated circuit of the electronic exchange according to claim 3, wherein 6. A buffer 11 'is connected with a transmission side gain control section 13' via a signal selection section 12 ', and the transmission side gain control section 13' is connected via an anti-aliasing filter 14 'to a charging signal removal section. 15 'are connected to the charging signal removing unit 15' via a band signal filter 16 'and a coder 17'.
2. The PCM CODEC integrated circuit of an electronic exchange according to claim 1, wherein the PCM CODEC integrated circuit 3'is configured in an array in which the above are connected. 7. The PCM C of the electronic exchange according to claim 6, wherein the transmission side gain control section 13 'is arranged between the charging signal removing section 15' and the band pass filter 16 '.
ODEC integrated circuit. 8. A transmission side gain section 13 'and a band pass filter 1
6 ′ and a digital filter and transmission side gain adjusting unit 30
PCM of the electronic exchange characterized by being placed between the charging signal removing unit 15 'and the coder 17'.
ODEC integrated circuit.